Continuing attempts to understand, diagnose, treat and prevent neural disorders rely, in part, on localization or imaging techniques, allowing researchers to determine the location, number and size of specific neurological phenomena. Among those sites undergoing specific testing are cocaine receptors associated with dopamine and serotonin transporter sites.
In order to be useful as a binding ligand for these types of imaging techniques, the compound must have a high affinity for the receptors in question. One such example is the tritiated compound [.sup.3 H]WIN 35,428, discussed in conjunction with the protocol for determining the relative affinity in binding ligands set forth in the presentation of Carroll et al, 19th Annual FASEB Meeting, Washington, D.C. (1990) incorporated herein-by-reference. Compounds exhibiting high affinity have previously been demonstrated to be useful as binding ligands, in in vitro and in vivo processes. Madras et al, Molecular Pharmacology, 36, 518-524 (1989) and Scheffel et al, Synapse, 4, 390-394 (1989) both incorporated by reference.
In processes of this type, a radioactively labeled, or similarly labeled compound is administered or injected, depending on in vivo or in vitro processing, and allowed to bind to the transporter sites in question. Thereafter, those sites actually bound to can be determined, by radiographic imaging techniques and the like. In one example, diagnosis of Parkinson's disease may be accomplished by administering a binding ligand having a high affinity for dopamine transporters, and subsequently subjecting the brain to SPECT scanning. The relative frequency of bound sites and imaging obtained allows an assessment of the presence or absence of Parkinson's disease.
Many radioactively labeled ligands, such as the tritiated compound discussed above, or other tritiated or carbon-14 labeled compounds lack sufficient specific activity or affinity are subject to specimen quenching and absorption. Additionally, ideal radiolabeled binding ligands should be useful in powerful scanning and imaging techniques, such as SPECT (Single Photon Emission Computed Tomography) scanning and the like. Thus, improved binding ligands exhibiting these advantages continue to be an object of those of skill in the art.